The invention relates to a stabilizing device for motor vehicles having pneumatically operated braking systems.
It is known to use an electronic stabilizing program (ESP in connection with an electronic braking system (EBS) for stabilizing motor vehicles. In the case of such an ESP, the vehicle is stabilized in critical situations by automatic wheel-selective brake interventions or by engine interventions. In the case of a passenger car ESP, the vehicle is stabilized, for example, during a beginning of a swerve, by automatic wheel-selective brake interventions as well as by engine interventions. When the instability of the vehicle starts, the measured vehicle movement will no longer correspond to the (intended) vehicle movement defined by the driver via the steering wheel. In this situation, the ESP stabilizes the vehicle by means of wheel-selective brake interventions and by means of engine interventions, so that the movement corresponds to the driver's intention—within physical possibilities. Thus, for example, during oversteering, the front wheel, which is on the outside during cornering, will mainly be braked and, during understeering, the rear wheel, which is on the inside during cornering, will mainly be braked. For this purpose, in addition to the ABS sensor system (rotational wheel speed sensors at each wheel), sensors are also used for the steering wheel angle (driver's intention) as well as for the yaw rate and the lateral acceleration of the vehicle (actual movement) (ABS=antilock system). In order to be able to stabilize the vehicle during braking by the driver, information concerning the driver's braking intention is additionally required.
The braking of a desired individual wheel of the vehicle can take place without any problem in the case of an EBS system as a result of its structure.
The ESP for commercial vehicles, currently for semitrailer units, represents a further development of the passenger car ESP in order to cover two additional degrees of freedom—jackknifing and overturning. It is based on an electronic braking system (EBS), which is expanded by ESP sensors (steering wheel angle, yaw rate and lateral acceleration). In this case, for stabilizing the vehicle combination at a low coefficient of friction (DSP function), for example, during oversteering, the entire semitrailer is braked in addition to the front wheel which is on the outside during cornering. As a result of the semitrailer control module, this becomes possible also for conventional semitrailers (equipped only with an ABS). At a middle and high coefficient of friction, a commercial vehicle tends to overturn more easily than swerve, which is why, in this case, the so-called ROP (roll-over protection) function will engage. In this case, when the vehicle threatens to overturn, the speed of the vehicle is reduced by engine and brake interventions to such an extent that the danger of overturning is clearly reduced.
German Patent Document DE 198 13 783 A1 shows a braking system for a vehicle, which achieves driving stability by means of relatively few actuators and by means of a complicated control system.
European Patent Document EP 0 482 374 A1 shows an electro-pneumatic braking system, in which signals of a steering wheel torque sensor are used for improving the vehicle stabilization.
German Patent Document DE 196 40 141 A1 shows a motor vehicle with a pneumatically operated braking system, in which brake cylinders are provided which have ABS pressure control valves. In this case, the ABS control valves are connected to a shuttle valve which, on the one hand, can be connected by way of a brake valve, which is operated by the driver and, on the other hand, by way of an electrically actuable shut-off valve with a compressed air supply. When a control device detects an instability, the brake cylinders are acted upon by compressed air by means of the shut-off valves in order to generate, to increase, or to reduce braking forces at vehicle wheels. As a result, the lateral control force of the vehicle wheels is influenced, and torques are generated about the vertical axis of the vehicle, which torques have the purpose of stabilizing the vehicle's movement. Nevertheless, in the case of vehicles equipped in this manner, dangerous situations may occur during the operation if these vehicles are operated with a trailer or semitrailer.
It is a disadvantage of such known systems that high costs are incurred occur for providing the corresponding actuators. In addition, the known systems have complicated constructions. Nevertheless, the U.S. market in particular has a demand for stabilizing systems, such as the ESP or ROP.
It is an object of the invention to provide an improved motor vehicle.
In this case, an ASR valve provides, in particular, the following functionality. When electrically controlled, the ASR valve switches the pressure at the input of the valve through to its output. When the control is switched off, the pressure at the output is reduced or is reduced and bled.
In this case, an ABS pressure control valve provides, in particular, the following functionality. It has two magnetic valves, one of which, when controlled, separates the pressure at the input from the output. When controlled, the other magnetic valve bleeds the output. Thus, a consuming device connected to the output can be acted upon by pressure in a selective and precise manner. The magnets can also be controlled in a pulsed operation.
An idea on which the invention is based meets the demands according to the task in a manner such that the existing components of an ABS and/or ASR system in a motor vehicle are utilized, such that an ESP function is thereby achieved. Additional components may be provided for this purpose.
Thus, at least one additional valve may be provided which, while bypassing the brake valve actuated by the driver, applies the storage pressure of the vehicle to the wheel valves of the individual brake cylinders. By means of the ABS valves provided at each wheel, which now can virtually only reduce the pressure, the respective pressure for the brake cylinders will then be controlled in the appropriate manner. If it promotes the stability of the vehicle that, on one side, a certain wheel is to be braked while the other wheel of the axle is to be rotated, this can be accomplished by shutting off the pressure on one side, and, on the other side, controlling a certain pressure in front of the corresponding wheel valve.
ABS systems comprise such wheel valves. However, an additional valve, which can control a brake pressure while bypassing the driver, does not exist in the ABS system.
In the case of the stability program according to the invention, the possibility is therefore provided to preferably brake each wheel of the traction vehicle, as well as of the trailer, individually and independently.
In order to make the existing ABS/ASR systems suitable for the ESP, several concepts or embodiments will be introduced in the following. All these have in common that ABS and/or ASR components are used for keeping costs as low as possible.
The invention can be used in a simple manner in the case of traction vehicles and trailers. As a result, an ESP is provided for motor vehicles with pneumatically operated braking systems, which has almost the same control and regulating possibilities as electromechanical ESP systems. When the engine timing is additionally acted upon, a simple and good stabilization can be achieved in this manner in many emergency situations.